Multiple choice

The average age of 20 boys in a class decreases by two months when one boy aged 18 years is replaced by a new boy. Find the age of the new boy.

  1. 17 years 10 months

  2. 14 years 8 months

  3. 14 years

  4. 12 years

  5. 10 years 6 months
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total age change = 20 boys * (-2 months) = -40 months. New boy = Old boy - 40 months. 18 years - 40 months = 18 years - 3 years 4 months = 14 years 8 months.

AI explanation

When one boy is replaced, the total decrease in age for the 20 boys to lower their average by two months is 20 times 2 months, which equals 40 months. The new boy must be 40 months younger than the 18-year-old boy he replaced. Converting 40 months to 3 years and 4 months, and subtracting this from 18 years gives the new boy's age as 14 years 8 months.

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